An instrument for recording continuously the relative abundance of gases in a three component mixture is described. High accuracy of analysis has been sacrificed in favor of high speed response since the instrument was designed primarily for use in the investigation of respiratory problems. An instantaneous change in gas composition will appear on the record with a lag of less than 0.2 second and will require approximately 0.1 second to settle on this new value.

A microwavepolarimeter is described which enables the determination of rotation of the plane of polarization of microwaves in the 3.2‐cm band. The transmitter‐analyzer utilizes klystron tube 723 A/B. The microwaves are fed into a horn which acts as a polarizing agent. The analyzer‐receiver consists of a horn antenna, rotatable wave guide, a crystal detector, and an indicator. The microwaves are rectified by a crystal rectifier, and are either detected by a microammeter, a galvanometer, or by an amplifier of appropriate design. Changes of angles of rotation can be detected if they are not less than 2° to 3°.

A simple projection system and film holder for taking photomicrographs of particle tracks in photographic emulsions of the type used for nuclear research is described. With this film holder a series of exposures covering a considerable length of the track image is obtained on a single film as adjacent segments of track are brought successively into sharp focus and recorded.

A high temperature x‐ray powder diffraction camera has been designed to yield patterns at temperatures in excess of 2500°K. The sample, in form of a wire, compacted rod, or contained (wherever suitable) in a thin walled quartz or ceramic tube, is heated indirectly by conduction and radiation in a thin walled molybdenum,tantalum, or platinumfurnace. The furnace is heated by high frequency (0.5 megacycles) eddy currents induced by a small induction coil. The cylindrically shaped furnace and the sample are held coaxially in the induction coil and slowly revolved. The specimen temperature is maintained constant to ±0.2 percent by an especially designed temperature regulator. A water‐cooled copper jacket with slots covered with metal foil to filter the diffracted x‐radiation surrounds the furnace and is used to protect the x‐ray film from heat and light. The temperature of the specimen is measured with a disappearing filament optical pyrometer at temperatures in excess of 1100°K and a platinum, platinum‐rhodium thermocouple at lower temperatures. The camera is either operated with a high vacuum or with an inert gas atmosphere.

A methane flow beta‐proportional counter has been designed to detect the high and low energy solid beta‐emitters used in tracer experiments. At present, both C14 and P32 are being counted. The use of a sintered‐glass Gooch crucible, both as a filter and sample holder, greatly simplifies the analytical technique involved in such experiments. The instrument is stable and the results are reproducible over long time periods.

Two new ionization methods of detecting flames are described for use in the measurement of flame speeds. In one the loading characteristics of a high frequency oscillator are utilized by causing the flame to pass through an oscillator tank coil. The second method employs the flame conductivity by placing two ring electrodes around the exterior of a combustion tube, and applying a d.c. voltage across them through a large series resistance. The voltage pulse created by either method when the flame passes the detector is used to trigger an electronic chronoscope.

Both methods have the distinct advantage over previous methods of flame detection in that the direct measurement of flame speeds can be made without the introduction of electrodes or wires into the combustion tube. The oscillator detector has the additional advantage that the point at which the measurement is made can be varied at will.

The efficiency of G‐M tubes for recording γ‐quanta is increased by insertion of concentric ring systems of metal between the wire and the cylinder. When the ring systems get suitable voltages, good plateaus and resolving times are obtained. The efficiency of a counter, which had 3 ring systems with 24 rings in each system, was 2.5 times that of a conventional counter of the same size. This means an increase of 6 times in γ—γ‐coincidence measurements. The efficiency of an improved tube (see note added in proof) is 3.2 times that of a conventional counter.

A description is given of a low angle x‐ray diffraction camera which incorporates both high resolution and facility in adjustment and alignment of components. A diffraction pattern of the low angle pattern of collagen photographed with this instrument is compared with a similar pattern photographed with commercially available equipment.